Essential Performance Attributes of Preapplied waterproofing

Transcription

1 Essential Performance Attributes of Preapplied waterproofing Craig Boucher, LEED AP Grace Construction Products 62 Whittemore Ave., Cambridge, MA Phone: Fax: t h R C I I n t e R n a t I o n a l C o n v e n t I o n a n d t R a d e S h o w M a R C h , B o u C h e R 3 3

2 Abstract The practice of installing waterproofing onto a soil retention system prior to pouring the concrete foundation is preapplied waterproofing. The presentation will address the challenges of preapplied waterproofing and identify some issues that result in failures of some waterproofing systems. Critical performance attributes of a preapplied waterproofing system namely bond-to-concrete and lateral water migration resistance will be identified to help ensure a successful, leak-free waterproofing system. The presenter will share the knowledge gained from more than 50 years of waterproofing product development and the technical issues that were addressed in the development process. Speaker Craig Boucher, LEED AP Grace Construction Products - Cambridge, MA CrAIG BoUCHer has worked in the construction product industry for over ten years. He currently holds the position of product manager of below-grade waterproofing at W.r. Grace. Craig has been involved in water management and the building envelope for most of his career. He has witnessed waterproofing testing at third-party labs and participates in the ASTM committees that developed the standards. He has a BS in civil engineering from Worcester polytechnic Institute and is a leed Accredited professional. 3 4 B o u C h e R 2 8 t h R C I I n t e R n a t I o n a l C o n v e n t I o n a n d t R a d e S h o w M a R C h ,

3 Essential Performance Attributes of Preapplied waterproofing BELOw-GRADE waterproofing BASICS to waterproofing systems adhered to structures that have already been built, while preapplied waterproofing is installed prior to building the structure. While both have their uses, preapplied waterproofing offers a unique set of advantages in certain applications. contact with the exterior of the foundation slab and walls. preapplied waterproofing is usually the only option for the area under the foundation slab, because the area is not excavated to allow for postapplied waterproofing. However, postapplied waterproofing can be used on vertical foundation walls when there is access around the foundation perimeter and the project team decides to excavate out from the perimeter. Figure 2 shows a combination of preapplied waterproofing below the slab and postapplied waterproofing on the vertical walls. For project sites that are confined or where excavation out from the perimeter of the site is not possible and/or desired, preapplied waterproofing will be installed at both the horizontal area, under the slab; protecting buildings from below-grade water ingress is a critical concern for structures of all types. preapplied waterproofing systems offer some important advantages in certain construction applications. But they must be specified and installed correctly to deliver maximum performance over the COMMON USES OF PREAPPLIED long term. What type of system is right for waterproofing your specific application? What are the key In horizontal applications, preapplied factors to consider when selecting a solu- waterproofing is installed onto the mud tion? The answers lie in understanding the slab or earth prior to placing the concrete essential attributes of an effective preap- foundation slab. In vertical applications, plied waterproofing system. the preapplied waterproofing is attached to The purpose of all below-grade water- the soil retention system, such as timber proofing is to protect the foundation and lagging (see Figure 1), prior to the complebuilding from water and moisture ingress. tion of the foundation walls. Typically, the Sources of potential water ingress include preapplied waterproofing will be directly in precipitation, groundwater higher than the lowest elevation of the foundation, or groundwater that fluctuates above the lowest elevation of the foundation. Water ingress due to waterproofing failures can create liability for all parties involved: the design team, the applicator, and the consultant. These parties are often responsible for costly and time-consuming repairs to both the waterproofing system and any resulting water damage in the building. Waterproofing the below-grade area of a building using a quality product installed correctly will help avoid these issues and costs and reduce potential liability for the project team. Waterproofing can be categorized into two main categories: postapplied and preapplied. As their names suggest, postapplied refers Figure 1 Preapplied waterproofing installed against timber lagging in a vertical application. 28th RCI InteRnatIonal ConventIon and trade Show MaRCh 14-19, 2013 BouCheR 35

4 leed rating system credits associated with minimizing excavation of greenfield sites and utilizing brownfield sites. THREE ESSENTIAL ATTRIBUTES A preapplied waterproofing system must demonstrate the following essential attributes: puncture- and tear-resistant (suitable for harsh construction site conditions) Ability to bond to concrete lateral water migration resistance Figure 2 Combination of preapplied waterproofing below the slab and postapplied waterproofing on the vertical walls. Figure 3 A new building is located between two existing developed areas that cannot be removed or excavated, requiring use of preapplied waterproofing at both the horizontal and the vertical areas of the below-grade foundation. and the vertical areas, outside of the foundation walls. These conditions are common in areas such as densely populated urban areas, tourist areas, and universities or other campus environments. Figure 3 illustrates such an example, where an existing building and parking area to either side of the new building site prevent excavation out from the perimeter of the building, necessitating preapplied waterproofing. preapplied waterproofing can also be used in cases where the project team wishes to maximize the usable area of the building by extending the footprint out to adjacent structures. Finally, preapplied waterproofing can be used when the team wishes to minimize the amount of soil required to be excavated both in previously undeveloped greenfield sites and in brownfield (contaminated) sites. This may be particularly advantageous in brownfield sites, where the costs to remediate excavated soil are significant. It is important to note that the manufacturer of the preapplied waterproofing system should be consulted on brownfield sites to ensure the system is suitable for the particular exposure conditions of the site. In addition to cost considerations, using preapplied waterproofing may help projects qualify for These attributes are all important to ensure the preapplied waterproofing system will work as intended. let s review each of these essential attributes in detail. PUNCTURE- AND TEAR- RESISTANT (SUITABLE FOR HARSH CONSTRUCTION SITE CONDITIONS) preapplied waterproofing systems must be able to hold up to harsh job site conditions. During construction, they will be subjected to foot traffic, and objects such as tools and rebar could be placed on top of the waterproofing. Construction trades will use the preapplied waterproofing system as their working surface to build the rebar cage for the concrete that will be placed on top of the waterproofing. Having a system with good puncture resistance is critical to preventing leak paths that allow water to travel through. ASTM e154 is a test method that evaluates puncture resistance. The test prescribes a blunt object being forced through a section of the waterproofing that is clamped into a frame. A testing apparatus that pushes the blunt object also measures the force in pounds or Newton required to puncture the waterproofing. puncture resistance and ASTM e154 can be referenced in a guide specification. resistance of 200 pounds or 890 Newton force for horizontal materials and 100 pounds or 445 Newton force for vertical materials have historically yielded successful results and are referenced in third-party, industry guide specifications. A preapplied waterproofing membrane can be exposed to stresses on the construction site from laborers on the waterproofing, from heavy equipment being rolled across the waterproofing on a dolly, as well as from the concrete placement itself. To resist tears from these stresses, the waterproofing 3 6 B o u C h e R 2 8 t h R C I I n t e R n a t I o n a l C o n v e n t I o n a n d t R a d e S h o w M a R C h ,

5 material must have good tensile strength and elongation properties. ASTM D412 is a test method that can be used to evaluate the tensile strength and elongation characteristics of the waterproofing material. ASTM D412 involves cutting a portion of the material into a standard shape and clamping the material into a testing device that can stretch or elongate the material to determine how much it will elongate before breaking. The testing equipment also measures the tensile strength that is applied to the material as it is stretched and records the maximum tensile strength achieved, measured in pounds per square inch or mega-pascal. These properties and ASTM D412 can be referenced in a guide specification. A tensile strength of 4,000 pounds per sq. in. or 27.6 mega-pascal and an elongation of 500% have historically yielded successful results for preapplied waterproofing materials. In addition to serving as a working surface on the job site for several trades, the preapplied waterproofing will also be exposed to the exterior conditions at the job site. It is essential to have a system that can stand up to these conditions and perform as intended to waterproof the below-grade area of the building. Sources used to confirm that the waterproofing system will perform as intended include bulletins from the manufacturer addressing these harsh conditions and a long, successful track record proving that the system is time-tested for the application. To help ensure positive results, a time period that the waterproofing system has been successfully utilized for preapplied waterproofing can be stated in the guide specification. preapplied waterproofing is subjected to harsh conditions. ensuring the preapplied waterproofing system is fit for its purpose in these harsh conditions and has a long track record of successful performance is the first step. Additional steps that could be used to help ensure a leak-free preapplied waterproofing installation include independent third-party inspection of the installed waterproofing system and electronic field vector mapping. These measures may help identify damage and voids in the waterproofing system and allow for repair prior to covering the installation with concrete. BOND TO CONCRETE For a preapplied waterproofing system to work effectively, it must remain bonded Figure 4 Degradation of the soil retention system and soil settlement result in the waterproofing system s being unsupported and unconfined. or adhered to the concrete. The preapplied waterproofing system is secured to a soil retaining system, such as timber lagging or sheet piles, in vertical applications and installed onto a mud slab or gravel base in horizontal applications. These substrates will typically not remain intact or in place over the life of the building. Therefore, a preapplied waterproofing system that bonds to the concrete that is applied against it is essential to ensure the waterproofing does not sag or fall away from the foundation walls and floor. Figure 4 shows a vertical timber lagging soil retention system and soil under the horizontal area. The soil under the building and the soil retention system may have an impact on the preapplied waterproofing system over the life of the building. The wood or timber lagging is below grade and surrounded by dirt and soil. over time, the lagging will likely degrade or rot. Any steel components of the soil retaining system are at risk of degrading due to corrosion. The soil under the slab may settle or fall away from the underside of the building. over time, the corrosion and degradation of the vertical soil retaining system and the soil under the building may settle due to rising and falling groundwater, degradation of organic material in the soil, and seismic activity. Therefore, the preapplied waterproofing system may be left unsupported and unconfined. If the preapplied waterproofing system is not bonded or adhered to the concrete, there is a risk that the waterproofing could sag and fall away. This may result in stresses on the system that could lead to tears or open/failed seams, creating gaps in the waterproofing for water to pass through. Materials that swell or expand in the presence of water to provide a gasket against water infiltration may be rendered ineffective as the vertical soil retention system and soil under the building no longer support and confine the swellable material. Bond to concrete can be referenced in guide specifications. ASTM D903 is a test method that measures the peel strength of a material to a substrate. A strip of the preapplied waterproofing is adhered to a substrate, such as the concrete foundation that will be applied against the waterproofing in the field, and the strip is peeled off of the substrate. The testing device measures the peel strength to concrete in pounds per inch or Newtons per meter. peel adhesion to concrete of at least 5 pounds per inch or 880 Newtons per meter have historically yielded successful results for preapplied waterproofing materials and are referenced in thirdparty, industry guide specifications. Currently, preapplied waterproofing technologies create a bond to concrete via either an adhesive or mechanical bond. An adhesive bond is created when an adhesive on the side of the waterproofing facing the concrete creates a continuous bond to the concrete when the concrete is placed against the waterproofing. It is important to note that the adhesive on the side of the waterproofing will be exposed to the construction process. Therefore, an adhesive that creates a bond to the concrete only when the concrete is placed against it, but is not sticky and tacky before the concrete is applied, is ideal to prevent construction 2 8 t h R C I I n t e R n a t I o n a l C o n v e n t I o n a n d t R a d e S h o w M a R C h , B o u C h e R 3 7

6 Figure 5 Photos of mechanical and adhesive bond to concrete. workers, equipment, dust, and debris from adhering to the preapplied waterproofing. A mechanical bond is created by fibers or profiles that become encased by the concrete when the concrete is placed onto the waterproofing. For both types of materials, a good practice is to have the installed preapplied waterproofing system inspected by a third party to help ensure the material is suitable to receive concrete. If the preapplied waterproofing system has debris on top of the membrane or is excessively dirty due to the construction process, a good bond to the concrete may not be achieved. Inspecting, repairing, and cleaning excessively dirty areas of the preapplied waterproofing system will help ensure the expected bond to concrete is achieved. Figure 5 shows an adhesive bond and mechanical bond to concrete. For the mechanically bonded material, the fibers stretch and eventually break as the material is peeled away from the concrete substrate. The mechanical bond looks different than the adhesive bond, which has a continuous adhesive layer between the concrete and the waterproofing membrane. This difference is important when considering the final critical attribute for preapplied waterproofing: lateral water migration resistance. remaining bonded to concrete over time is important to ensure that the benefits of a fully bonded preapplied water- proofing system are realized. The track record of the waterproofing system can be evaluated to help understand if the bond to concrete will be maintained. Some preapplied waterproofing materials have been successfully used for over 20 years, which demonstrates that the system will perform as intended. Accelerated aging and longterm laboratory tests can help provide evidence that the waterproofing system will remain bonded over time, but a successful track record of actual performance in situ is the best indicator that the product will perform as intended over time. LATERAL water MIGRATION RESISTANCE lateral water migration resistance occurs when water is not allowed to travel between the preapplied waterproofing and the concrete foundation wall and floor to which the waterproofing is adhered. Figure 6A shows a proper installation of a preapplied waterproofing system prior to rebar placement, with no apparent voids or punctures in the system that could allow water passage. Figure 6B shows rebar being placed on top of the installed preapplied waterproofing system. During rebar installation, there is some risk that the preapplied waterproofing system could be damaged, punctured, or torn. In order to achieve a good bond between the preapplied waterproofing membrane and the concrete, the preapplied waterproofing membrane must be in direct contact with the concrete. Therefore, protection board cannot be installed on top of the preapplied waterproofing membrane to help prevent rebar punctures. Figure 6 Properly installed preapplied waterproofing (6A, above) and rebar installed on top of the preapplied waterproofing system (6B, right). 38 BouCheR 28th RCI InteRnatIonal ConventIon and trade Show MaRCh 14-19, 2013

7 Figure 7 Breaches or voids are shown in the waterproofing membrane with cracks or water entry points in the concrete a distance away from the breach or void. other trades on the job site could damage the preapplied waterproofing system as well, creating breaches and voids in the system. Inspection of the waterproofing system after installation and before the concrete placement is a good practice to catch any breaches and voids in the system before it is covered. However, in addition to inspection, a preapplied waterproofing system with good lateral water migration resistance can further reduce the likelihood of leaks into the building. Should water enter through a breach or void in the waterproofing system, lateral water migration resistance will prevent it from traveling to a crack or cold joint in the concrete that will allow water into the building. Figure 7 shows a membrane with a breach or void in both the vertical and horizontal membrane surfaces. Some distance away from the breach or void is a crack in the concrete. As precipitation occurs, water impacts the ground surrounding the building and can travel through the soil and down the vertical face of the below-grade wall. Also, groundwater may be present at a level above the lowest elevation of the foundation floor, or the groundwater may fluctuate and rise. eventually, the water will reach the breaches or voids in the membrane. If the 28th RCI InteRnatIonal ConventIon and water is free to move laterally between the membrane and the concrete, the water may get to the crack in the concrete and enter into the building, as shown in Figure 8. For preapplied waterproofing systems that prevent lateral water migration, a breach or void in the waterproofing system would have to be aligned with a crack or cold joint in the concrete for water entry into the building to occur. If leaks should occur, repairing the leak with an injectable grout from the inside of the building is the typical remedy. Because the waterproofing prevents lateral water migration, repairing the area of water leakage will be the extent of the repair. For membranes that do not prevent lateral water migration, the repair may be more extensive and costly, because water will continue to travel laterally between the membrane and the concrete and eventually find another entry point through the concrete and into the building. Chasing the leak from one entry point through the concrete to the next will require more time and material to try to repair the leak, and the task may be neverending if new cracks and cold joints in the concrete occur over time. lateral water migration resistance prevents the water from traveling between the preapplied waterproofing system and the concrete, reducing the likelihood of leaks into the building. This makes lateral water migration resistance a critical attribute of an effective preapplied waterproofing system. BONDING METHOD AND LATERAL water MIGRATION RESISTANCE earlier, we noted that the difference between a mechanical bond and an adhesive bond with the concrete affects lateral water migration performance. Mechanical bonds, using fibers that become encased in the poured concrete, typically do not prevent lateral water migration. The water can move between the mechanically bonded material and the concrete because the intermittent Figure 8 Water from precipitation or groundwater entering into a breach or void in the waterproofing, traveling between the waterproofing and concrete interface and entering the building. trade Show MaRCh 14-19, 2013 BouCheR 39

8 size, and a hole was cut in the center of the material to replicate a breach or void such as a rebar puncture. Metal pipes were placed on top of the materials and held firmly against the top of the material to prevent concrete from entering the bottom of the metal pipes. The metal pipes provide an open channel for water to pass through the concrete, simulating a crack or other path of water entry through a concrete foundation wall or floor. Concrete was placed onto the materials and allowed to cure. The test specimen represents a condition where there is a void or breach in the preapfigure 9 An isometric view from the bottom and a plied waterproofing material section view of the test specimens showing the path and there is an open chanof lateral water migration and water leakage into a nel through the concrete that building. could allow water entry into a building. The test specimens are then clamped into fibers do not provide a continuous adhesive a test apparatus specified in ASTM D5385. bond to prevent lateral water migration. This statement is supported by an inde- Water is pumped into the testing apparapendent, third-party laboratory analysis of tus at various pressures. Figure 9 shows technologies currently available and mar- two views of keted as preapplied waterproofing materi- the test specials, testing their lateral water migration mens. The top image is an resistance and bond to concrete. ASTM D5385, Standard Test Method for isometric view Hydrostatic Head, was used as a basis for from the botthe lateral water migration resistance test- tom, and the ing. Samples of the materials were cut to image at the bottom is a section view. The orange material is the preapplied waterproofing material being evaluated with concrete on top of the material and metal pipes passing through the concrete. During the test, water is introduced to the bottom of the test specimen where there is a void or breach in the waterproofing material. If the water travels laterally between the top of the waterproofing material and the bottom of the concrete, the water will reach the metal pipes and leak out of the specimen. Water used in the test was dyed green to confirm that water coming out of the pipes is the same water introduced to the test specimen. Figure 10 shows one of the materials evaluated in the test apparatus, with green water leaking out of the metal pipes, indicating lateral water migration has occurred. The second part of the third-party laboratory analysis was to measure bond to concrete. Bond to concrete was measured by running an ASTM D903 peel adhesion test on the test specimens. Figure 11 shows preapplied waterproofing materials being peeled off of concrete that was cast on top of the material. The test specimens were clamped to the bottom of the test apparatus, and the clamp at the top of the apparatus pulled the material up and off of the concrete. The performance of the evaluated materials is summarized in Figure 12. The first column is the material or product reference code. The middle two columns show the results of the lateral water migration resistance test (run by exposing the materials to Figure 11 Photos of peel adhesion testing of two specimens. Figure 10 A test specimen that allowed water with green dye to migrate laterally and leak through the specimen, failing the lateral water migration resistance testing. 40 BouCheR 28th RCI InteRnatIonal ConventIon and trade Show MaRCh 14-19, 2013

9 THE IMPORTANCE OF A FULLSYSTEM APPROACH Figure 12 Results of the third-party laboratory analysis. increasing levels of water pressure measured in pounds per sq. in.; 1 pound per sq. in. is equivalent to 2.31 ft. of hydrostatic head); the third column provides the equivalent hydrostatic head to which the product was exposed. products A and B are membranes that adhesively bond to concrete and are similar products (product A is intended for horizontal areas, and product B is intended for vertical walls). products C through H have a fabric or fleece on the side of the membrane in contact with the concrete, intended to provide a mechanical bond. As you will note in the chart, only the adhesively bonded membranes provided good lateral water migration resistance results. The last column in Figure 12 provides the results of the adhesion to concrete test. The adhesively bonded membranes yielded better results than the mechanically bonded membranes. lateral water migration resistance and the modified version of the ASTM D5385 could be referenced in guide specifications to help ensure that the preapplied waterproofing material being specified will work as intended to protect the building from water ingress. Figure 13A soil-retention system tieback. It is commonly said that a system is only as good as its weakest link. This is certainly true for preapplied waterproofing. The detail areas of the system such as corners or penetrations are areas prone to leak. Taking a full-system approach to below-grade waterproofing can help reduce the risk of leaks at these areas. As noted earlier, a horizontal preapplied waterproofing system below the building can be used with a postapplied waterproofing system on the vertical walls. Utilizing a single source for both waterproofing materials helps ensure product compatibility and typically enables the designer to use a standard detail that has been successfully used previously and is provided by the manufacturer. Having one source for all the waterproofing will also eliminate questions about which product manufacturer is at fault if there are leaks at the tie-in detail. The detail areas of a preapplied waterproofing project may require several steps, and performance of the installed detail is often highly dependent on the skill of the installer. Using preformed details can reduce labor costs and ensure continuity Figure 13C Prefabricated tieback cover detail. Figure 13B Field-fabricated tieback cover detail. 28th RCI InteRnatIonal ConventIon and trade Show MaRCh 14-19, 2013 BouCheR 41

10 of the waterproofing system. Furthermore, applying preformed details that prevent lateral water migration and bond to concrete are important in the details areas, and it is recommended that the preformed details be capable of providing those attributes. Ultimately, preformed details can reduce the risk of leaks and liability due to leaks in the detail areas. Use of preformed details can be written into the guide specification to ensure they are used and the benefits are realized. one typical example of a prefabricated detail is a soil retention system tieback cover. The soil retention system tiebacks protrude beyond the interior plane of the soil retention system. often, the tiebacks are covered with a field-fabricated sheetmetal box, and then the waterproofing system is applied over the sheet metal box. Figures 13A, 13B, and 13C show that there are several steps and several layers of the waterproofing material installed to ensure a watertight installation. The preformed tieback cover dome shown in Figure 13C is one piece that is made watertight at the factory. This preformed detail reduces labor time and helps ensure a watertight installation. CONCLUSION: PERFORMANCE MATTERS In summary, we have covered what preapplied waterproofing is and its use in circumstances when access to the outside or exterior side of the foundation is not feasible. We discussed the essential attributes of preapplied waterproofing: that it needs to be durable and fit for harsh job site conditions and, most importantly, that it must prevent lateral water migration and bond to concrete. As with all waterproofing, it is best if the preapplied waterproofing system is fully bonded to the structure it is waterproofing. We discussed a third-party laboratory analysis demonstrating that adhesively bonded waterproofing membranes outperformed the evaluated mechanically bonded preapplied membranes. We covered the advantages of a full-system approach to preapplied waterproofing, using a single source for all the waterproofing components and using preformed, prefabricated details to help avoid risk of leaks at the critical and labor-intensive detail areas. putting all of these principles into practice will lead to a preapplied waterproofing solution that, when installed correctly, reduces the risk of water ingress and minimizes the risk of liability for all parties involved in the project. And that s the ultimate measure of performance. 4 2 B o u C h e R 2 8 t h R C I I n t e R n a t I o n a l C o n v e n t I o n a n d t R a d e S h o w M a R C h ,